(a) Field of the Invention
This invention relates generally to a communications system and method wherein multiple communication systems are integrated into a common allocated radio frequency spectrum. More particularly, it relates to a communications system and method that integrates a terrestrial communication system into the radio frequency spectrum allocated to a mobile satellite communication system.
(b) Description of Related Art
Terrestrial communication services such as voice cellular and Personal Communication Systems (PCS) transmit information within a narrow spectrum surrounding nominal frequencies of 900 MHZ and 2 GHz respectively. The available spectra for such terrestrial communications are scarce and expensive. To operate their businesses profitably, companies providing these terrestrial communication services must maximize the number of users on their allocated frequency spectrum. This is accomplished by first sub-dividing the allocated spectrum into numerous spectra or frequency bands, and then sub-dividing large geographic areas into numerous spatially isolated communication cells. Thus, each cell can support numerous users on its multiple frequency bands, and reuse of these frequency bands across cells permits multiple users to use the same frequency band as long as they are in spatially isolated cells.
Mobile Satellite Service (MSS) providers such as the American Mobile Satellite Corporation (AMSC) provide satellite communication services through networks of mobile satellites in geosynchronous earth orbit (GEO). Other MSS providers operate satellite networks in medium earth orbit (MEO), and low earth orbit (LEO). The Federal Communications Commission (FCC) has allocated a 34 MHZ spectrum within the L-band (at ≈1.5 GHz) for use in mobile satellite communications. MSS providers share this 34 MHZ spectrum globally. As with the terrestrial communication providers, MSS providers can improve their profitability by maximizing the number of users on their allocated frequency spectrum. Traditionally, this has been accomplished using specific antenna designs and locations that provide spatial or geographic isolation and then reusing frequency bands across the isolated areas.
Thus, there is a need for a system and method of integrating multiple communication systems into a common allocated radio frequency spectrum. More specifically, there is a need for a system and method that integrates a terrestrial communication system into the radio frequency spectrum allocated to a mobile satellite communication system.
In accordance with one aspect of the present invention, a terrestrial communication system comprises a terrestrial cell site that produces a signal at a satellite uplink frequency and transmits it to a terrestrial user terminal, and that receives a signal at a satellite downlink frequency that was transmitted by a terrestrial terminal unit.
In accordance with another aspect of the present invention, a terrestrial communication system comprises a terrestrial terminal unit that produces a signal at a satellite downlink frequency and transmits it to a terrestrial cell site, and that receives a signal at a satellite uplink frequency that was transmitted by a terrestrial cell site.
In accordance with yet another aspect of the present invention, a method of integrating a terrestrial communication system into a satellite communication frequency spectrum comprises the following steps: a) producing a signal at a satellite uplink frequency that is transmitted from a terrestrial cell site to a terrestrial user terminal, and b) receiving a signal at a satellite downlink frequency that was produced by said terrestrial user terminal and transmitted to a terrestrial cell site.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.